1. Field of the Invention
The present invention relates to a command-controllable integrated circuit (IC) memory device such as a flash memory and, also, to a method for determining the operational compatibility of the IC memory device with a host system.
2. Description of the Prior Art
FIG. 9 is a block diagram of a conventional IC memory device using M5M29F016 flash memory manufactured by Mitsubishi Denki Kabushiki Kaisha. Note that this IC memory device 100 is used in the form as connected to a host system 110 that controls operation of the IC memory device 100. A manufacturer code and device code, which are used for determining whether the host 110 is operationally compatible with the IC memory device 100, are stored at a specific address in the status/ID register 103 of the flash memory. In the example shown, the manufacturer code 1Ch, for example, is stored at address 000000h, and the device code DAh is stored at address 000001h.
The operating mode of the IC memory device 100 is set using commands written to the command user interface (CUI) 102 by the host 110. One method whereby the host 110 can determine the compatibility of the IC memory device 100 is to apply a specific command, for example, a command 90h in this example, to the CUI 102 of the IC memory device 100 to read the manufacturer code 1Ch and the device code DAh from the status/ID register 103.
The host 110 then determines whether the IC memory device 100 is compatible based on the manufacturer code 1Ch and the device code DAh returned from the IC memory device 100. It should be noted that the device codes used for this determination are not limited to codes defined by the Joint Electron Device Engineering Council (JEDEC), and can be any particular code system. The code size is also not specifically limited.
There are cases, however, in which the manufacturer code 1Ch and the device code DAh are set to different values in different IC memory devices that operate according to the same algorithm, use the same commands, and are operationally compatible. An example of such a case is an IC memory device that has been simply reduced in size. The host 110 must therefore recognize these as different IC memory devices, even though the operating algorithms are the same, and devices which are identical in every way except for the manufacturer are assigned different, discrete manufacturer and device codes.
A problem with this method of determining device compatibility is that as a result of using the manufacturer and device codes to determine operational compatibility, a host 110 must specifically recognize the device code of every device with which it is compatible, that is, a potentially large number of codes.
A further problem is that for a host 110 to use the latest IC memory devices, it must also be compatible with the latest manufacturer and device codes.
It should be noted that Japanese Patent Laid-Open Publication No. 57-6491 teaches a semiconductor device that internally compares an identification code written to ROM with an internal identification code, and outputs a specific value when the comparison matches. Note, however, that this semiconductor device does not exchange identification code information with the host.
Note, further, that Japanese Patent Laid-Publication 6-259982 teaches a method and apparatus for rewriting a flash ROM device with the objective of preventing rewrite errors by comparing internal fixed information with information in the rewrite request signal applied from an external device, and returning a specific value to the external device when a match is confirmed.
There is therefore a need for IC memory whereby it can be determined in the IC memory whether the memory is compatible with the manufacturer and device codes of the host.
There is also a need for IC memory whereby compatibility can be determined without it being necessary for the host to store manufacturer and device codes for every IC memory device with which it is compatible.
There is a further need for IC memory whereby host operation can be simplified, and a method for determining operational compatibility of IC memory addressing these needs.